Internal combustion engines utilize feedback from exhaust gas oxygen sensors to maintain desire air-fuel ratio mixtures during combustion, at least under some conditions. Various types of exhaust gas oxygen sensors may be used, such as linear type sensors (sometimes referred to as UEGO sensors), and switching type sensors (sometimes referred to as EGO, or HEGO, sensors, depending on whether a heater is included).
The inventors herein have recognized that under some conditions, it may be advantageous to utilize a switching type sensor, such as when operating about stoichiometry, as it may be possible to have a more accurate identification of stoichiometry through operating conditions and sensor aging. Further, it may be advantageous to utilize a linear type sensor, such as when operating away from stoichiometry (e.g., lean), as it may be possible to have a more accurate identification of air-fuel ratios over a broader range. However, the additional costs of adding sensors typically forces selection of a single sensor type for any given exhaust location, at least in some systems.
One approach that attempts to use both types of sensor places one type of sensor upstream of a catalyst, and another type of sensor downstream of the catalyst. See, for example, U.S. Pat. Nos. 6,567,738 and 5,832,724. However, the inventors herein have recognized that whichever selection is made, each has disadvantages, such as noted above. Further, these disadvantages can be exacerbated when operating in a partial cylinder deactivation condition, where some cylinders operate with combustion, and others operate in a fuel cut condition.
The above issue may be addressed by, in one example, a system for a vehicle traveling on the road. The system comprises: a first cylinder; a second cylinder; a linear exhaust gas sensor coupled exclusively to said first cylinder; a switching exhaust gas sensor coupled exclusively to said second cylinder; and a controller configured to operate in a first mode with both said first and second cylinders carrying out lean combustion, where fuel injection amounts to each of said first and second cylinder are adjusted based on said linear sensor; said controller further configured to operate in a second mode with both said first and second cylinders carrying out combustion about stoichiometry, where fuel injection amounts to at least one of said first and second cylinder are adjusted based on said switching sensor.
In another example, a system for a vehicle traveling on the road is provided. The system comprises: a first cylinder; a second cylinder; a linear exhaust gas sensor coupled exclusively to said first cylinder; a switching exhaust gas sensor coupled exclusively to said second cylinder; and a controller configured to operate in a first mode with said first cylinder carrying out lean combustion and said second cylinder operating without injected fuel, where fuel injection amounts to said first cylinder are adjusted based on said linear sensor; said controller further configured to operate in a second mode with said second cylinder carrying out combustion about stoichiometry and said first cylinder operating without injected fuel, where fuel injection amounts to said second cylinder are adjusted based on said switching sensor.
In this way, when operating in a stoichiometric partial cylinder cut operation, a switching type sensor can be both upstream of a catalyst and isolated from the air pumped through the fuel cut cylinders. Likewise, when operating in lean partial cylinder cut operation, a linear type sensor can also be upstream of a catalyst.
Further, it is also possible to obtain the advantage of each type of sensor when operating with both cylinders carrying out combustion in either a lean or stoichiometric mode. For example, the linear type sensor can be used during lean combustion to control both cylinder groups. Likewise, the switching type sensor can be used during stoichiometric combustion to control both cylinder groups.